There are indeed a few scenarios which are not resolved by priority rules on unmarked intersections. Assuming brown wants to go straight on this is one of them, because there is an additional rule which says that you need to give way to traffic on the same road continuing in a straight line. This means green needs to give way to brown (and brown to red, red to green).
There is also the general concept that priority is something you receive, not something you take. Dutch law defines 'giving way' ('voorrang verlenen') as 'Allowing the other driver to proceed unhampered.' This assigns a duty to to the vehicle that must give way, but does not grant any rights to the other vehicle. They are still bound by the catch all rule to (Art. 5) requiring them to not create danger and not impede traffic.
So, everybody needs to stop (or at least almost stop) to allow someone else to proceed, if you don't you broke the law. However, once you've done that you've complied, even if the other car does not proceed. The law does not not require to wait until the other driver finally decides to proceed, quite the opposite, you should proceed when it's safe to do so to not impede traffic. (If all drivers would just sit there and wait they are technically all breaking the law because they are impeding traffic.)
In practice, situations like this resolve themselves either when someone is polite and waves others through, or when someone is bold and starts going. In low traffic and/or low speed intersections this works fine in practice. And generally intersections where this might cause issues will have specific priority rules.
In this specific case I'd expect brown to go first, as there seems to be some common understanding that it's sensible to clear the cars that go in a straight line first. But there is no rule in the law which dictates that.